#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>

struct TreeNode 
{
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
};
 


struct TreeNode* invertTree(struct TreeNode* root)
{
    if (root == NULL)
        return NULL;
    struct TreeNode* mid = root->left;
    root->left = invertTree(root->right);
    root->right = invertTree(mid);
    return root;
}